Not sure why. but i can confirm for a fact the origional Doom 3 on xbox had co op support. but it was for sure taken out of the xbox 360 version of doom3 in the bfg edition. which is really crap. I cant say for sure if the origional doom 3 for pc would have the co op tho. really sad, it was awesome.

That mod team used iD's engine, iD's art assets + Quake 4 SDK to build their mod ? You make it sound as if they made their mod from scratch, using their own engine, and their own assets, and thus, they entitled to not give back to the community.

As a matter of fact, all they did was networking existing entities, copying Quake 4 projectiles code and some other stuff, added their maps and bam!, coop is ready.

So, please give me a reason to believe source code of that mod should be kept private.